Manufacturing method, manufacturing apparatus, and mold unit for resin container

ABSTRACT

A manufacturing method of a resin container includes: a first injection molding process for injection-molding a first layer of a preform having a bottomed cylindrical shape by using a first resin material; a second injection molding process for injecting a second resin material having a color that is different from a color of the first resin material, and laminating a second layer on an outer peripheral side or an inner peripheral side of the first layer; and a blow-molding process for blow-molding a preform that includes multiple layers and has been obtained in the second injection molding process in a state where residual heat at a time of injection molding is contained, and manufacturing the resin container having a color pattern that corresponds to a thickness distribution of the first layer and the second layer.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a manufacturing method, a manufacturingapparatus, and a mold unit of a resin container.

Description of the Related Art

It is requested that containers that accommodate cosmetics, milkylotion, or the like have the visually attractive appearance of thecontainers themselves, in order to enhance the buying intention ofconsumers. As this type of containers that accommodate cosmetics or thelike, a bottle that is made of glass, creates luxurious feeling ormassive feeling, and can maintain a beautiful state in repetitive usehas been preferably used. In addition, in order to improve the estheticappearance of containers, it is desired that a gradation pattern havinga change in a shade of color be applied to containers that accommodatecosmetics or the like.

Meanwhile, bottles made of glass are heavy and fragile, and also have ahigh transportation cost or manufacturing cost. Therefore, it has beenconsidered that as containers that accommodate cosmetics or the like, abottle made of glass is replaced with a resin container.

As one example of a manufacturing method of a resin container, a hotparison blow-molding method is conventionally known. In the hot parisonblow-molding method, a resin container is blow-molded by using residualheat at the time of injection molding of a preform. Therefore, there isan advantage in which a variety of resin containers that have excellentesthetic appearance can be manufactured in comparison with a coldparison method.

In addition, in a case where a gradation pattern is formed in a resincontainer, the technique described below has been proposed. For example,JP S61-59984 B discloses a technology for fitting an outer shell piecethat is colored transparent and has a difference in thicknessdistribution into an inner shell piece to form a multilayer preform, andforming a gradation pattern in a container after blow-molding inaccordance with the thickness distribution of the outer shell piece.

For example, WO 2004/022307 A discloses a technology for simultaneouslyinjection-molding plural types of resin materials in coextrusion to forma multilayer preform, and forming a gradation pattern in a containerafter blow-molding. In the technology of WO 2004/022307 A, amounts ofextrusion of the resin materials at the time of injection molding arecontrolled, and this causes a change in thickness of each layer that isrequired in the gradation pattern.

In the technology of JP S61-59984 B, if each of the pieces is notsufficiently cooled down to have a certain degree of hardness, the twopieces fail to be fitted into each other to form a preform. Statedanother way, the technology of JP S61-59984 B fails to be applied to ahot parison blow-molding method, and processes from injection molding ofa preform to blow-molding of a container fail to be completed in a shorttime.

In addition, in the technology of WO 2004/022307 A, in practice, it isvery difficult to precisely control a change in thickness in each of thelayers of the preform in coextrusion. Further, some types of patternsfail to be reproduced in coextrusion. Therefore, in the technology ofPatent Literature 2, it is still difficult to stably form a desiredcolor pattern in a container after blow-molding.

SUMMARY OF THE INVENTION

A manufacturing method of a resin container in one aspect of the presentinvention includes: a first injection molding process forinjection-molding a first layer of a preform having a bottomedcylindrical shape by using a first resin material; a second injectionmolding process for injecting a second resin material having a colorthat is different from a color of the first resin material, andlaminating a second layer on an outer peripheral side or an innerperipheral side of the first layer; and a blow-molding process forblow-molding a preform that includes multiple layers and has beenobtained in the second injection molding process in a state whereresidual heat at a time of injection molding is contained, andmanufacturing the resin container having a color pattern thatcorresponds to a thickness distribution of the first layer and thesecond layer.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are vertical sectional views of preforms having amultilayer structure according to the present embodiment.

FIGS. 2A and 2B are diagrams illustrating examples of a resin containeraccording to the present embodiment.

FIG. 3 is a diagram schematically illustrating a configuration of ablow-molding apparatus according to the present embodiment.

FIGS. 4A and 4B are diagrams illustrating a process of manufacturing apreform in a first example.

FIGS. 5A to 5C are diagrams illustrating a process of manufacturing apreform in a second example.

FIG. 6 is a flowchart illustrating processes of a containermanufacturing method.

FIGS. 7A to 7C are explanatory diagrams of a first variation of thepresent embodiment.

FIGS. 8A to 8C are explanatory diagrams of a second variation of thepresent embodiment.

FIGS. 9A to 9C are explanatory diagrams of a third variation of thepresent embodiment.

FIG. 10 is a diagram schematically illustrating a configuration of ablow-molding apparatus according to another embodiment.

FIG. 11 is a flowchart illustrating processes of a containermanufacturing method according to the other embodiment.

DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present invention are described below with referenceto the drawings.

In the embodiments, in order to make description easily understandable,description is provided in a state where a structure or elements otherthan a principal portion of the present invention are simplified oromitted. In addition, in the drawings, the same element is denoted bythe same reference sign. Note that a shape, a size, or the like of eachelement in the drawings is schematically illustrated, and does notindicate an actual shape, size, or the like.

Configuration Examples of Preform

First, configuration examples of a preform having a multilayer structureaccording to the present embodiment are described with reference to FIG.1 .

FIG. 1A is a vertical sectional view of a preform 10 in a first exampleof the present embodiment, and FIG. 1B is a vertical sectional view of apreform 10 in a second example of the present embodiment.

Both the entire shapes of the preforms 10 illustrated in FIGS. 1A and 1Bare a bottomed cylindrical shape in which one end side is open andanother end side is closed. These preforms 10 include a barrel 14 thathas been formed in a cylindrical shape, a bottom 15 that closes theother end side of the barrel 14, and a neck 13 that has been formed inan opening on the one end side of the barrel 14. In addition, thesepreforms have a multilayer structure in which a second layer 12 has beenlaminated on a first layer 11. The first layer 11 and the second layer12 that have been described above are formed by performing two stages ofinjection molding, as described later.

In the preform 10 in the first example illustrated in FIG. 1A, the neck13 has been formed in the first layer 11 that is located on an innerperipheral side, and the second layer 12 has been laminated on an outerperipheral side from the barrel 14 to the bottom 15 of this first layer11.

In the preform 10 in the second example illustrated in FIG. 1B, the neck13 has been formed in the first layer 11 that is located on an outerperipheral side, and the second layer 12 has been laminated on an innerperipheral side from the barrel 14 to the bottom 15 of this first layer11. In the preform 10 in the second example, a hole 16 has been formedin a center of a bottom of the first layer 11, and the hole 16 of thefirst layer 11 is closed by the second layer 12 from the inside.

As illustrated in FIGS. 1A and 1B, these preforms 10 include a taperedregion 17 in which a thickness of the second layer 12 graduallydecreases in an axis direction from a bottom side to a neck side. Forexample, the tapered region 17 is formed in a portion on an upper sidein the drawing that faces the neck side in the second layer 12. Thistapered region 17 has a configuration in which a thickness t2 of asecond portion of the second layer 12 that is closer to the neck 13 thana first portion of the second layer 12 is smaller than a thickness t1 ofthe first portion. Note that the specifications, such as a shape or asize, of the first layer 11 and the second layer 12 are appropriatelyadjusted according to a shape of a container to be manufactured, a colorpattern to be formed in the container, or the like.

Hereinafter, a resin material that is used to form the first layer 11 isalso referred to as a first resin material, and a resin material that isused to form the second layer 12 is also referred to as a secondmaterial.

Both the first resin material and the second resin material are athermoplastic synthetic resin, and can be appropriately selectedaccording to the specifications of a container. Specific examples of atype of material include polyethylene terephthalate (PET), polyethylenenaphthalate (PEN), polycyclohexanedimethylene terephthalate (PCTA),Tritan (registered trademark) (copolyester from Eastman ChemicalCompany), polypropylene (PP), polyethylene (PE), polycarbonate (PC),polyethersulfone (PES), polyphenylsulfone (PPSU), polystyrene (PS),cyclic olefin polymer (COP/COC), polymethyl methacrylate (PMMA: acryl),polylactic acid (PLA), nylon, and the like. An additive such as colorantcan be appropriately added to these resin materials.

In addition, in each of the preforms 10 described above, resin materialsthat are different in color are employed in the first layer 11 and thesecond layer 12. For example, the first resin material and the secondresin material are different in an amount of colorant (a shade of color)or a type of colorant (a type of color). Colorant does not need to beadded to one of the first resin material and the second resin material.

In addition, both or at least one of the first layer 11 and the secondlayer 12, for example, a layer including a portion that faces an outerperiphery, may have a property that allows light to pass through (alight transmissive property). Note that a layer having the lighttransmissive property may be colored. The present embodiment isdescribed under the assumption that the first resin material istransparent (has the light transmissive property).

In addition, a combination of the first resin material and the secondmaterial can be appropriately set according to the specifications of acontainer, and it is preferable that materials having high mutualweldability be combined. As an example, the first resin material and thesecond resin material may be resin materials that have differentcompositions of colorant and are of the same type (for example, PETs).

Configuration Examples of Resin Container

Next, configuration examples of a resin container (hereinafter alsosimply referred to as a container) according to the present embodimentare described with reference to FIGS. 2A and 2B.

FIG. 2A is a diagram illustrating an example of a container 20 obtainedby blow-molding the preform 10 in the first example, and FIG. 2B is adiagram illustrating an example of a container 20 obtained byblow-molding the preform 10 in the second example. In each of FIGS. 2Aand 2B, a right half portion of the drawing illustrates the appearanceof the container 20, and a left half portion of the drawing illustratesa vertical cross section of the container 20.

In the containers 20 of FIGS. 2A and 2B, for example, skin lotion, milkylotion, or the like is accommodated. The container 20 includes a neck 21that includes an opening at an upper end, a barrel 22 that continuouslyextends from the neck 21 and has a cylindrical shape, and a bottom 23that continuously extends from the barrel 22.

In addition, in the barrel 22 of the container 20, three regions (afirst region 22 a, an intermediate region 22 b, and a second region 22c) are formed along the axis direction, and therefore a gradationpattern in which a shade of color gradually changes in the axisdirection is applied. By applying decoration having such a pattern, theesthetic appearance of the container 20 is improved, and the buyingintention of consumers can be further enhanced in the use as a cosmeticcontainer or the like.

First, the neck 21 and the first region 22 a including an upper sideportion of the barrel 22 are formed by using the first layer 11.Therefore, the color of the first layer 11 appears in the neck 21 or thefirst region 22 a of the barrel 22.

On the other hand, the bottom 23 and the second region 22 c including alower side portion of the barrel 22 are formed by laminating the firstlayer 11 and the second layer 12. Therefore, in the bottom 23 or thesecond region 22 c of the barrel 22, the color of the second layer 12that is located in an outer periphery appears in the case of FIG. 2A, orthe color of the second layer 12 on an inner layer side appears throughthe first layer 11 in the case of FIG. 2B.

Between the first region 22 a and the second region 22 c, theintermediate region 22 b formed by stretching the tapered region 17 ofthe preform 10 is provided. In this intermediate region 22 b, thethickness of the second layer 12 gradually decreases in a direction froma bottom side to a neck side. Therefore, in the intermediate region 22b, color gradually changes in the axis direction according to athickness ratio of the first layer 11 and the second layer 12.Specifically, a ratio of the first layer 11 increases in a positioncloser to the neck side, and therefore the intermediate region 22 b hasa color that is close to the color of the first region 22 a. Incontrast, a ratio of the second layer 12 increases in a position closerto the bottom side, and therefore the intermediate region 22 b has acolor that is close to the color of the second region 22 c.

Note that the barrel 22 of the container 20 may be formed to have athickness that is much smaller than the thickness of the bottom 23, andthe barrel 22 may have a uniform thickness distribution. If thecontainer 20 is formed to have a shape having the thickness distributiondescribed above, luxurious feeling or massive feeling is emphasized, andthe container 20 can be made closer to a consumer’s impression of acosmetic container.

Description of Container Manufacturing Apparatus

FIG. 3 is a diagram schematically illustrating a configuration of ablow-molding apparatus according to the present embodiment. Ablow-molding apparatus 30 according to the present embodiment is anexample of a container manufacturing apparatus, and employs a hotparison method (also referred to as a one-stage method) for blow-moldingthe container 20 by utilizing residual heat (a quantity of internalheat) at the time of injection molding without cooling down the preform10 to room temperature.

The blow-molding apparatus 30 includes a first injection molding unit31, a second includes molding unit 32, a temperature adjusting unit 33,a blow-molding unit 34, an taking out unit 35, and a conveyancemechanism 36. The first injection molding unit 31, the second injectionmolding unit 32, the temperature adjusting unit 33, the blow-moldingunit 34, and the taking out unit 35 are disposed in positions that havebeen displaced in a rotating manner by every predetermined angle (forexample, every 72 degrees) with the conveyance mechanism 36 as a center.

Conveyance Mechanism 36

The conveyance mechanism 36 includes a transfer plate (not illustratedin FIG. 3 ) that rotates about an axis in a sheet vertical direction inFIG. 3 as a center. On the transfer plate, a neck mold 36 a (notillustrated in FIG. 3 ) that holds the neck 13 of the preform 10 (or theneck 21 of the container 20) is disposed. In a case where the transferplate includes a single roughly disk-shaped member, one or more neckmolds 36 a are disposed at every predetermined angle. In a case wherethe transfer plate includes roughly fan-shaped members that have beendivided for respective molding units, one or more neck molds 36 a aredisposed for each of the divided transfer plates.

The conveyance mechanism 36 rotates the transfer plate, and thereforethe conveyance mechanism 36 conveys the preform 10 (or the container 20)in which a neck is held by the neck mold 36 a to the first injectionmolding unit 31, the second injection molding unit 32, the temperatureadjusting unit 33, the blow-molding unit 34, and the taking out unit 35in this order. Accordingly, each of the neck molds 36 a is shared by aplurality of molding stations (at least the first injection molding unit31 and the second injection molding unit 32). In addition, a taperedpart 36 a 1 has been formed on an outside face (or an inside face) ofthe neck mold 36 a. The tapered part 36 a 1 comes into contact with oris fitted into a mold of each of the molding stations, and therefore arelative positional relationship between both parts at the time ofmolding can be regulated. Note that the conveyance mechanism 36 can alsoelevate or lower the transfer plate, and also performs an operationrelating to mold closing or mold opening (mold releasing) in the firstinjection molding unit 31 or the second injection molding unit 32.

First Injection Molding Unit 31

The first injection molding unit 31 includes a mold for first injectionmolding that includes a cavity mold 40, a core mold 41, and a hot runnermold 42, and manufactures the first layer 11 of the preform 10. Thefirst injection molding unit 31 is connected to a first injection device37 that supplies the first resin material to the hot runner mold 42. Thecavity mold 40 includes a fitting part (a concavo-convex part forfitting and a position regulation part) 40 b on a face on an oppositeside of a face that faces the hot runner mold 42 (see FIG. 4A and FIGS.5A and 5B). The fitting part 40 b includes a tapered part 40 b 1 havinga shape that is roughly similar to a shape of the tapered part 36 a 1 ofthe neck mold 36 a, and receives the tapered part 36 a 1 of the neckmold 36 a by using the tapered part 40 b 1.

FIG. 4A illustrates a first injection molding unit 31 a that molds thefirst layer 11 of the preform 10 in the first example (FIG. 1A). FIGS.5A and 5B illustrate a first injection molding unit 31 b that molds thefirst layer 11 of the preform 10 in the second example (FIG. 1B). Notethat herein, when the first injection molding units 31 a and 31 b do notneed to be distinguished from each other, the first injection moldingunit 31 is used as a generic term.

As illustrated in FIG. 4A and FIG. 5A, in the first injection moldingunit 31, mold closing is performed on the cavity mold 40, the core mold41, and the neck mold 36 a of the conveyance mechanism 36 that have beendescribed above, and a mold space (a molding space) of the first layer11 is formed.

The cavity mold 40 illustrated in FIG. 4A specifies an outer peripheralshape of an inner layer (the first layer 11) of the preform 10. The coremold 41 illustrated in FIG. 4A is inserted into the cavity mold 40, andspecifies an inner peripheral shape of the inner layer.

On the other hand, the cavity mold 40 illustrated in FIGS. 5A or 5Bspecifies an outer peripheral shape of an outer layer (the first layer11) of the preform 10. The core mold 41 illustrated in FIGS. 5A or 5B isinserted into the cavity mold 40, and specifies an inner peripheralshape of the outer layer.

Then, the first resin material is poured into the mold space describedabove through the hot runner mold 42 from the first injection device 37,and therefore the first layer 11 of the preform 10 is manufactured inthe first injection molding unit 31.

In addition, as illustrated in FIG. 4A, in a position of a barrel of thecavity mold 40 of the first injection molding unit 31 a, a region 40 ain which a diameter decreases in a position closer to a bottom side hasbeen formed. Therefore, in the first layer 11 formed by the firstinjection molding unit 31 a, a region where a thickness changes in atapered manner is formed on an outer peripheral side.

In addition, as illustrated in FIG. 5B, in the first injection moldingunit 31 b, a valve pin 43 that can move in the axis direction to aposition close to the core mold 41 is provided in the interior of thehot runner mold 42. The valve pin 43 is accommodated in the interior ofthe hot runner mold 42 until the mold space is filled with the firstresin material, and the valve pin 43 protrudes to a position close tothe core mold 41 after the mold space has been filled with the firstresin material. The valve pin 43 moves at the time of injection molding,as described above, and therefore a thin film 18 in which the thicknessof a resin material is smaller than the thickness of a peripheral partcan be formed in a center of the bottom of the first layer 11.

In addition, even when mold opening has been performed on the firstinjection molding unit 31, the neck mold 36 a of the conveyancemechanism 36 is not opened, and in this state, the first layer 11 of thepreform 10 is held and conveyed. The number of preforms 10 to besimultaneously molded by the first injection molding unit 31 (that is,the number of containers 20 that can be simultaneously molded by theblow-molding apparatus 30) can be appropriately set.

Second Injection Molding Unit 32

The second injection molding unit 32 includes a mold for secondinjection molding that includes a cavity mold 50, a core mold 51, and ahot runner mold 52, and the second injection molding unit 32injection-molds the second layer 12 in an outer peripheral part or aninner peripheral part of the first layer 11. The second injectionmolding unit 32 is connected to a second injection device 38 thatsupplies the second resin material to the hot runner mold 52. Inaddition, the cavity mold 50 includes a fitting part (a positionregulation part) 50 b on a face on an opposite side of a face that facesthe hot runner mold 52 (see FIG. 4B and FIG. 5C). The fitting part 50 bincludes a tapered part 50 b 1 having a shape that is roughly similar toa shape of the tapered part 36 a 1 of the neck mold 36 a, and receivesthe tapered part 36 a 1 of the neck mold 36 a by using the tapered part50 b 1.

FIG. 4B illustrates a second injection molding unit 32 a that molds thesecond layer 12 of the preform 10 in the first example (FIG. 1A). FIG.5C illustrates a second injection molding unit 32 b that molds thesecond layer 12 of the preform 10 in the second example (FIG. 1B). Notethat herein, when the second injection molding units 32 a and 32 b donot need to be distinguished from each other, the second injectionmolding unit 32 is used as a generic term.

The second injection molding unit 32 a accommodates the first layer 11of the preform 10 that has been injection-molded by the first injectionmolding unit 31 a. As illustrated in FIG. 4B, in a state where moldclosing has been performed on the second injection molding unit 32 a, amold space is formed between a portion from the barrel to the bottom ofthe outer peripheral side of the first layer 11 and an inner face of thecavity mold 50.

The core mold 51 illustrated in FIG. 4B is inserted into an inner layer(the first layer 11) of the preform 10, and holds the inner layer fromthe inside. The cavity mold 50 illustrated in FIG. 4B receives the innerlayer into which the core mold 51 will be inserted, forms a mold spaceof an outer layer (the second layer 12) between the cavity mold 50 andan outer peripheral face of the inner layer, and specifies an outerperipheral shape of the outer layer.

The mold space described above is filled with the second resin materialfrom the second injection device 38 by using the hot runner mold 52, andtherefore the second layer 12 is formed on the outer peripheral side ofthe first layer 11. In this second layer 12, the tapered region 17 inwhich a diameter increases in a position closer to the bottom side isformed due to a relationship with the thickness of the first layer 11.By doing this, the preform 10 in the first example is manufactured.

The second injection molding unit 32 b accommodates the first layer 11of the preform 10 that has been injection-molded by the first injectionmolding unit 31 b. As illustrated in FIG. 5C, in a state where moldclosing has been performed on the second injection molding unit 32 b, amold space is formed between a portion from the barrel to the bottom ofthe inner peripheral side of the first layer 11 and a surface of thecore mold 51.

The cavity mold 50 illustrated in FIG. 5C receives an outer layer (thefirst layer 11) of the preform 10, and holds the outer layer from theoutside. The core mold 51 illustrated in FIG. 5C is inserted into aninside of the outer layer, forms a mold space of an inner layer (thesecond layer 12) between the core mold 51 and an inner peripheral faceof the outer layer, and specifies an inner peripheral shape of the innerlayer.

The second injection device 38 fills the mold space described above withthe second resin material by using the hot runner mold 52, and thereforethe second layer 12 is formed on the inner peripheral side of the firstlayer 11. By doing this, the preform 10 in the second example ismanufactured.

In addition, as illustrated in FIG. 5C, a region 51 a in which adiameter decreases in a position closer to the bottom side has beenformed in the core mold 51 of the second injection molding unit 32 b.Therefore, in the second layer 12 formed by the second injection moldingunit 32 b, the tapered region 17 where a thickness changes can beformed.

Temperature Adjusting Unit 33

The temperature adjusting unit 33 includes a not-illustrated mold fortemperature adjustment (a temperature adjusting pot or a temperatureadjusting core). The temperature adjusting unit 33 accommodates thepreform 10 conveyed from the second injection molding unit 32 in themold for temperature adjustment in which temperature is maintained at apredetermined temperature, and therefore the temperature adjusting unit33 makes temperature uniform or removes temperature deviation, andadjusts the temperature of the preform 10 to a temperature suitable forfinal blowing (for example, about 90° C. to 105° C.). In addition, thetemperature adjusting unit 33 also has a function of cooling down thepreform 10 in a high-temperature state after injection molding. Notethat the temperature adjusting pot includes a fitting part (a positionregulation part) that comes into contact with the neck mold 36 a and canbe fitted, and the fitting part includes a tapered part having a shapethat is roughly similar to a shape of the tapered part 36 a 1 of theneck mold 36 a.

Blow-Molding Unit 34

The blow-molding unit 34 performs blow-molding on the preform 10 inwhich temperature has been adjusted by the temperature adjusting unit33, and manufactures the container 20.

The blow-molding unit 34 includes a mold for blow-molding that includesblow cavity molds that are a pair of split molds that correspond to ashape of the container 20, a bottom mold, and a stretching rod and anair introducing member (a blowing core, both are not illustrated). Theblow-molding unit 34 performs blow-molding while stretching the preform10. This causes the preform 10 to be shaped into a shape of the blowcavity mold, and the container 20 can be manufactured. The pair of blowcavity molds include a fitting part (a position regulation part) thatcomes into contact with the neck mold 36 a and can be fitted, and thefitting part includes a tapered part having a shape that is roughlysimilar to a shape of the tapered part 36 a 1 of the neck mold 36 a.

Taking out unit 35

The taking out unit 35 is configured to release the neck 21 of thecontainer 20 manufactured by the blow-molding unit 34 from the neck mold36 a, and take out the container 20 to an outside of the blow-moldingapparatus 30. The taking out unit 35 includes an taking out rod (a moldfor taking out) that is inserted from an opening of the neck mold 36 a.The taking out rod includes a fitting part (a position regulation part)that can roughly abut onto the neck mold 36 a.

Description of Container Manufacturing Method

Next, a container manufacturing method performed by the blow-moldingapparatus 30 according to the present embodiment is described. FIG. 6 isa flowchart illustrating processes of the container manufacturingmethod.

Step S101: First Injection Molding Process

First, as illustrated in FIG. 4A and FIG. 5A, in the first injectionmolding unit 31, the first resin material is injected from the firstinjection device 37 into a mold space formed by the cavity mold 40, thecore mold 41, and the neck mold 36 a of the conveyance mechanism 36, andthe first layer 11 of the preform 10 is molded. In a case where thepreform 10 in the first example is formed, the first injection moldingunit 31 a is used, and in a case where the preform 10 in the secondexample is formed, the first injection molding unit 31 b is used.

In the first injection molding unit 31 b, as illustrated in FIG. 5B,after the first layer 11 of the preform 10 has been molded, a process ofcausing the valve pin 43 to protrude to a position close to the coremold 41 is performed. By doing this, in the center of the bottom of thefirst layer 11, the thin film 18 having a thickness that is smaller thana thickness of a peripheral part is formed.

Then, when mold opening has been performed on the first injectionmolding unit 31, the transfer plate of the conveyance mechanism 36rotates by a predetermined angle, and the first layer 11 of the preform10 held by the neck mold 36 a is conveyed to the second injectionmolding unit 32 in a state where residual heat at the time of injectionmolding is contained.

Step S102: Second Injection Molding Process

Next, the first layer 11 of the preform 10 is accommodated in the secondinjection molding unit 32, and the second layer 12 is injection-molded.In a case where the preform 10 in the first example is formed, thesecond injection molding unit 32 a is used, and in a case where thepreform 10 in the second example is formed, the second injection moldingunit 32 b is used.

In the second injection molding unit 32 a, as illustrated in FIG. 4B, amold space is formed between a portion from the barrel to the bottom ofthe outer peripheral side of the first layer 11 and the cavity mold 50that faces an outer periphery of the first layer 11. The mold spacedescribed above is filled with the second resin material by using thehot runner mold 52.

In FIG. 4B, the core mold 51 is inserted on the inner peripheral side ofthe first layer 11, and the core mold 51 holds a shape of the firstlayer 11 from the inner peripheral side. Therefore, even if the secondresin material comes into contact with the first layer 11, heatdeformation of the first layer 11 can be avoided. In a case where thepreform 10 in the first example is molded by doing the above, the secondlayer 12 can be formed on the outer peripheral side of the first layer11.

In contrast, in the second injection molding unit 32 b, as illustratedin FIG. 5C, a mold space is formed between a portion from the barrel tothe bottom of the inner peripheral side of the first layer 11 and thecore mold 51 that faces an inner periphery of the first layer 11. Themold space described above is filled with the second resin material byusing the hot runner mold 52. Note that the thin film 18 has been formedin the bottom of the first layer 11. However, the thin film 18 is brokendue to injection pressure of the second resin material, a hole 16 isformed in the bottom, and the second resin material is guided from thehole 16 described above to the inner peripheral side of the first layer11.

In FIG. 5C, the cavity mold 50 faces the outer peripheral side of thefirst layer 11, and the cavity mold 50 holds a shape of the first layer11 from the outer peripheral side. Therefore, even if the second resinmaterial comes into contact with the first layer 11, heat deformation ofthe first layer 11 can be avoided. In a case where the preform 10 in thesecond example is molded by doing the above, the second layer 12 can beformed on the inner peripheral side of the first layer 11.

Note that the first layer 11 in the second injection molding process hasresidual heat at the time of injection molding, and is relatively easilydeformable. Therefore, if the second resin material is injected into themold space, air in the mold space is pushed out in an upward directionwhile slightly elastically deforming the first layer 11, and isexhausted. Thus, air accumulation is not likely to be generated at thetime of molding the second layer 12, and this avoids defective moldingof the preform 10.

As described above, by performing the first injection molding processand the second injection molding process, the preform 10 in the firstexample or the second example is manufactured.

Then, when mold opening has been performed on the second injectionmolding unit 32, the transfer plate of the conveyance mechanism 36rotates by a predetermined angle, and the preform 10 held by the neckmold 36 a is conveyed to the temperature adjusting unit 33 in a statewhere residual heat at the time of injection molding is contained.

Step S103: Temperature Adjusting Process

Next, in the temperature adjusting unit 33, the preform 10 isaccommodated in a mold unit for temperature adjustment, and temperatureadjusting process is performed to make the temperature of the preform 10closer to a temperature suitable for final blowing. Then, the transferplate of the conveyance mechanism 36 rotates by a predetermined angle,and the preform 10 after temperature adjustment that has been held bythe neck mold 36 a is conveyed to the blow-molding unit 34.

Step S104: Blow-Molding Process

Next, in the blow-molding unit 34, the container 20 is blow-molded.

First, mold closing is performed on the blow cavity mold to accommodatethe preform 10 in mold space, and the air introducing member (theblowing core) is lowered, and therefore the air introducing member abutsonto the neck 13 of the preform 10. Then, the stretching rod is lowered,the bottom 15 of the preform 10 is pressed down from an inner face, andblowing air is supplied from the air introducing member while performinglongitudinal-axis stretching as needed, and therefore lateral-axisstretching is performed on the preform 10. By doing this, the preform 10swells out and is shaped to come into close contact with the mold spaceof the blow cavity mold, and the container 20 is blow-molded. Note thatin a case where the preform 10 is longer than the container 20, thebottom mold is caused to stand by in a lower position that does not comeinto contact with the bottom of the preform 10 before mold closing ofthe blow cavity mold, and is quickly elevated to a molding positionafter mold closing.

In addition, in the present embodiment, the preform 10 in the firstexample or the second example is blow-molded, and therefore a container20 having a gradation pattern in which a shade of color graduallychanges in an axis direction according to stretching of the first layer11 and the second layer 12 is manufactured.

Step S105: Container Taking out Process

When blow-molding has been finished, mold opening is performed on theblow cavity mold. This enables the container 20 to move from theblow-molding unit 34.

Next, the transfer plate of the conveyance mechanism 36 rotates by apredetermined angle, and the container 20 is conveyed to the taking outunit 35. In the taking out unit 35, the neck 21 of the container 20 isreleased from the neck mold 36 a, and the container 20 is taken out toan outside of the blow-molding apparatus 30.

By doing the above, a single cycle of the container manufacturing methodterminates. Then, by rotating the transfer plate of the conveyancemechanism 36 by a predetermined angle, the respective processesdescribed above of S101 to S105 are repeated. Note that during theoperation of the blow-molding apparatus 30, five containers aremanufactured in parallel at every time difference of a single process.

In addition, for the sake of a structure of the blow-molding apparatus30, respective time periods of the first injection molding process, thesecond injection molding process, the temperature adjusting process, theblow-molding process, and the container taking out process have the samelength. Similarly, time periods of conveyance between the respectiveprocesses have the same length.

As described above, in the present embodiment, in the first injectionmolding process, a first layer 11 of a preform 10 is injection-molded,and in the second injection molding process, a second layer 12 isinjection-molded in an inner peripheral part or an outer peripheral partof the first layer 11, and a preform 10 having a multilayer structure ismanufactured. In the present embodiment, each of the first layer 11 andthe second layer 12 of the preform 10 having a multilayer structure ismolded in two stages of injection molding, and therefore shapes andthickness distributions of the first layer 11 and the second layer 12can be precisely controlled. This enables a desired gradation pattern tobe stably formed in a container 20 by performing internal coloring.

In addition, in the present embodiment, a preform 10 having a multilayerstructure is manufactured in two stages of injection molding, thepreform 10 is blow-molded in a state where residual heat at the time ofinjection molding is contained, and a container 20 is manufactured. Thesecond layer of the preform 10 includes a tapered region 17 in which athickness gradually decreases in an axis direction from a bottom side toa neck side. Then, the preform 10 described above is blow-molded in astate where residual heat at the time of injection molding is contained,and therefore a container 20 having a gradation pattern in which a shadeof color gradually changes in the axis direction according to stretchingof the first layer 11 and the second layer 12 is manufactured.

For example, in comparison with a case where cooled preforms are fitted,a preform having a multilayer structure is manufactured, and afterreheating, blow-molding is performed (a cold parison method), in thecase of the present embodiment, a preform does not need to be cooleddown to a temperature close to ordinary temperature, and neither is aprocess of assembling or reheating the preform needed. Therefore,according to the present embodiment, a series of processes frominjection molding of a preform 10 to blow-molding of a container 20 canbe completed in a relatively short time, and a container 20 having agradation pattern can be manufactured in a shorter cycle.

Variations

FIGS. 7A to 9C are diagrams that explain a first variation to a thirdvariation of the embodiment described above. In the respectivevariations described below, it is assumed that a preform having a shapeof an inverted paraboloid of revolution is blow-molded, and a container20 is manufactured. A basic configuration of a blow-molding apparatus 30in the variations is similar to a basic configuration in the embodimentdescribed above.

FIGS. 7A to 7C are explanatory diagrams of the first variation in whicha container 20 having a horizontal-striped color pattern 24 ismanufactured. FIG. 7A is a vertical sectional view of a cavity mold 60that forms a first layer of a preform, and FIG. 7B is a plan view of thecavity mold 60 of FIG. 7A. In addition, FIG. 7C is a front view of thecontainer 20 in the first variation.

In the first variation, at least two or more annular protrusions (orstepped protrusions) 61 a and 61 b have been concentrically formed on aninner face of the cavity mold 60 that forms the first layer. Note thatall of the protrusions of a cavity mold 60 in each of the variationshave been formed to be a draft. By doing this, an annular recess isformed on an outer face of the first layer of the preform. If a resinmaterial having a different color is injection-molded on an outerperipheral side of this first layer to form a second layer, the secondlayer gets in the recess of the first layer, and a preform (notillustrated) including an annular thick portion formed by using thesecond layer can be manufactured. By blow-molding this preform, asillustrated in FIG. 7C, a container 20 having a horizontal-striped colorpattern 24 that corresponds to a thickness distribution of the firstlayer and the second layer can be manufactured.

FIGS. 8A to 8C are explanatory diagrams of the second variation in whicha container 20 having a spiral color pattern 25 is manufactured. FIG. 8Ais a vertical sectional view of a cavity mold 60 that forms a firstlayer of a preform, and FIG. 8B is a plan view of the cavity mold 60 ofFIG. 8A. In addition, FIG. 8C is a front view of the container 20 in thesecond variation.

In the second variation, a swirling protrusion 61 c has been formed onan inner face of the cavity mold 60 that forms the first layer. By doingthis, a swirling recess is formed on an outer face of the first layer ofthe preform. If a resin material having a different color isinjection-molded on an outer peripheral side of this first layer to forma second layer, the second layer gets in the recess of the first layer,and a preform (not illustrated) including a swirling thick portionformed by using the second layer can be manufactured. By blow-moldingthis preform, as illustrated in FIG. 8C, a container 20 having a spiralcolor pattern 25 that corresponds to a thickness distribution of thefirst layer and the second layer can be manufactured.

FIGS. 9A to 9C are explanatory diagrams of the third variation in whicha container 20 having a color pattern 26 of an arbitrary pattern, suchas a character, is manufactured. FIG. 9A is a vertical sectional view ofa cavity mold 60 that forms a first layer of a preform, and FIG. 9B is aplan view of the cavity mold 60 of FIG. 9A. In addition, FIG. 9C is afront view of the container 20 in the third variation.

In the third variation, a protrusion 61 d having an arbitrary pattern(the character “A”) has been formed on an inner face of the cavity mold60 that forms the first layer. By doing this, a recess having a shape ofthe pattern described above is formed on an outer face of the firstlayer of the preform. If a resin material having a different color isinjection-molded on an outer peripheral side of this first layer to forma second layer, the second layer gets in the recess of the first layer,and a preform (not illustrated) including a thick portion having a shapeof the pattern described above by using the second layer can bemanufactured. By blow-molding this preform, as illustrated in FIG. 9C, acontainer 20 having a color pattern 26 having a shape of the patterndescribed above that corresponds to a thickness distribution of thefirst layer and the second layer can be manufactured.

The present invention is not limited to the embodiment described above,and various improvements and changes in design may be made withoutdeparting from the spirit of the present invention.

In the present embodiment, an example has been described where a preform10 having a two-layer structure is molded in two stages of injectionmolding, and this preform 10 is blow-molded. However, in a blow-moldingapparatus 30 according to the present invention, an injection moldingunit may be further added, and a preform having an n-layer structure maybe molded in n-stages of injection molding (where n is an integer of 3or more). By doing this, a container having a color pattern of morecomplicated color arrangement can be manufactured. Note that in a casewhere three or more injection molding units are provided, in order toadjust the temperature of residual heat in each layer to a preferabletemperature, a temperature adjusting unit may be appropriately addedbetween the injection molding units.

In addition, in the embodiment described above, a configuration exampleof what is called a five-station type blow-molding apparatus 30 has beendescribed. However, a blow-molding apparatus according to the presentinvention may be a six-station type blow-molding apparatus that includesa temperature adjusting unit that auxiliarily heats or cools down thefirst layer 11 of the preform 10, between the first injection moldingunit 31 and the second injection molding unit 32.

FIG. 10 is a diagram schematically illustrating a configuration exampleof a six-station type blow-molding apparatus 30 a serving as anotherembodiment. In addition, FIG. 11 is a flowchart illustrating processesof a container manufacturing method according to the other embodiment.Note that in the description below of the other embodiment, a duplicatedescription relating to an element that is similar to an element of theembodiment described above is appropriately omitted.

The blow-molding apparatus 30 a illustrated in FIG. 10 includes a firstinjection molding unit 31, a temperature adjusting unit 39 (a firsttemperature adjusting unit), a second injection molding unit 32, atemperature adjusting unit 33 (a second temperature adjusting unit), ablow-molding unit 34, an taking out unit 35, and a conveyance mechanism36. The first injection molding unit 31, the temperature adjusting unit39, the second injection molding unit 32, the temperature adjusting unit33, the blow-molding unit 34, and the taking out unit 35 are disposed inpositions that have been displaced in a rotating manner by everypredetermined angle (for example, every 60 degrees) with the conveyancemechanism 36 as a center.

The conveyance mechanism 36 of the blow-molding apparatus 30 a includesa transfer plate 36 b that rotates about an axis in a sheet verticaldirection in FIG. 10 as a center. The transfer plate 36 b conveys thepreform 10 (or the container 20) in which a neck is held by a neck moldto the first injection molding unit 31, the temperature adjusting unit39, the second injection molding unit 32, the temperature adjusting unit33, the blow-molding unit 34, and the taking out unit 35 in this order.

In addition, the temperature adjusting unit 39 has a configuration thatis roughly similar to a configuration of the temperature adjusting unit33, and includes a not-illustrated mold for temperature adjustment (atemperature adjusting pot or a temperature adjusting core). Thetemperature adjusting unit 39 accommodates the first layer 11 of thepreform 10 conveyed from the first injection molding unit 31 in a moldunit that is maintained at a predetermined temperature, and thereforethe temperature adjusting unit 39 auxiliarily heats or cools down thefirst layer 11.

As illustrated in FIG. 11 , a container manufacturing method performedby the blow-molding apparatus 30 a according to the other embodiment isdifferent from the manufacturing method according to the embodimentdescribed above illustrated in FIG. 6 in that a first temperatureadjusting process (S101 a) is performed between the first injectionmolding process (S101) and the second injection molding process (S102).

In the first temperature adjusting process (S101 a), in the temperatureadjusting unit 39, the first layer 11 of the preform 10 is accommodatedin the mold unit for temperature adjustment, the first layer 11 iscooled down, and a temperature distribution is adjusted (temperature ismade uniform, or temperature deviation is removed). At this time, in thetemperature adjusting unit 39, the first layer 11 may be heated asneeded.

Then, the transfer plate 36 b of the conveyance mechanism 36 rotates bya predetermined angle, and the first layer 11 of the preform 10 held bythe neck mold is conveyed to the second injection molding unit 32. Notethat the other processes in FIG. 11 are similar to processes in FIG. 6 .

In addition, it is to be considered that the embodiments disclosedherein are exemplary, and are not restrictive in all points. The scopeof the present invention is specified by the claims rather than thedescription above, and is intended to include all changes withoutdeparting from equivalent meaning and scope of the claims.

1. A manufacturing method of a resin container, the manufacturing methodcomprising: a first injection molding process for injection-molding afirst layer of a preform having a bottomed cylindrical shape by using afirst resin material; a second injection molding process for injecting asecond resin material having a color that is different from a color ofthe first resin material, and laminating a second layer on an outerperipheral side or an inner peripheral side of the first layer; and ablow-molding process for blow-molding a preform that includes multiplelayers and has been obtained in the second injection molding process ina state where residual heat at a time of injection molding is contained,and manufacturing the resin container having a color pattern thatcorresponds to a thickness distribution of the first layer and thesecond layer.
 2. The manufacturing method of the resin containeraccording to claim 1, wherein the preform manufactured in the secondinjection molding process includes a region where a thickness ratio ofthe first layer and the second layer changes in a predetermineddirection, and the resin container has a gradation pattern formed bystretching the region.
 3. The manufacturing method of the resincontainer according to claim 1 wherein in the second injection moldingprocess, a core mold that holds a shape of the first layer is insertedinto the inner peripheral side of the first layer, and the second resinmaterial is injected between a cavity mold and the first layer, thecavity mold facing the outer peripheral side of the first layer.
 4. Themanufacturing method of the resin container according to claim 1 whereinin the second injection molding process, a cavity mold that holds ashape of the first layer is disposed on the outer peripheral side of thefirst layer, and the second resin material is injected between a coremold and the first layer, the core mold facing the inner peripheral sideof the first layer.
 5. The manufacturing method of the resin containeraccording to claim 4, wherein in the first injection molding process, athin film having a small thickness is formed in a portion of the firstlayer, and in the second injection molding process, the thin film isbroken by injecting the second resin material, and the second resinmaterial is guided to the inner peripheral side of the first layer. 6.The manufacturing method of the resin container according to claim 1,wherein the first resin material and the second resin material are resinmaterials that have different compositions of colorant and are of anidentical type.
 7. A manufacturing apparatus of a resin container, themanufacturing apparatus comprising: a first injection molding unitconfigured to a first layer of a preform having a bottomed cylindricalshape by using a first resin material; a second injection molding unitconfigured to inject a second resin material having a color that isdifferent from a color of the first resin material, and laminates asecond layer on an outer peripheral side or an inner peripheral side ofthe first layer; and a blow-molding unit configured to blow-mold apreform that includes multiple layers and has been obtained in thesecond injection molding process in a state where residual heat at atime of injection molding is contained, and manufactures the resincontainer having a color pattern that corresponds to a thicknessdistribution of the first layer and the second layer.
 8. A mold unitthat is used in a manufacturing apparatus that includes a firstinjection molding unit and a second injection molding unit configured tomold a preform including multiple layers, and a blow-molding unitconfigured to blow-mold the preform including the multiple layers andmanufacture a resin container, the mold unit comprising: a first moldconfigured to be used in the first injection molding unit that forms aninner layer having a bottomed cylindrical shape of the preform; and asecond mold configured to be used in the second injection molding unitthat laminates an outer layer of the preform on an outside of the innerlayer, wherein the first mold includes: a first cavity mold configuredto specify an outer peripheral shape of the inner layer; and a firstcore mold configured to be inserted into the first cavity mold, andspecify an inner peripheral shape of the inner layer, the second moldincludes: a second core mold configured to be inserted into the innerlayer, and hold the inner layer from an inside; and a second cavity moldconfigured to receive the inner layer into which the second core mold isinserted, forms a mold space of the outer layer between the secondcavity mold and an outer peripheral face of the inner layer, and specifyan outer peripheral shape of the outer layer, and the first cavity moldhas a shape including a diameter decreasing portion where a diameter ofan outer periphery of the inner layer decreases in a position closer toa bottom.
 9. A mold unit that is used in a manufacturing apparatus thatincludes a first injection molding unit and a second injection moldingunit configured to mold a preform including multiple layers, and ablow-molding unit configured to blow-mold the preform including themultiple layers and manufactures a resin container, the mold unitcomprising: a first mold configured to be used in the first injectionmolding unit that forms an outer layer of the preform; and a second moldconfigured to be used in the second injection molding unit thatlaminates an inner layer having a bottomed cylindrical shape of thepreform on an inside of the outer layer, wherein the first moldincludes: a first cavity mold configured to specify an outer peripheralshape of the outer layer; and a first core mold configured to beinserted into the first cavity mold, and specify an inner peripheralshape of the outer layer, the second mold includes: a second cavity moldconfigured to the outer layer, and hold the outer layer from an outside;and a second core mold configured to be inserted into the inside of theouter layer, forms a mold space of the inner layer between the secondcore mold and an inner peripheral face of the outer layer, and specifyan inner peripheral shape of the inner layer, and the second core moldhas a shape including a diameter decreasing portion where a diameter ofan outer periphery of the inner layer decreases in a position closer toa bottom.
 10. The mold unit according to claim 8, further comprising: aneck mold configured to be shared by at least the first injectionmolding unit and the second injection molding unit, grasp a moldedobject of the first injection molding unit, and convey the molded objectto the second injection molding unit, wherein each of the first cavitymold and the second cavity mold includes a position regulation part thatregulates a position of the neck mold.
 11. The mold unit according toclaim 10, further comprising a third mold configured to beused in aprocess of the manufacturing apparatus that is different from the firstinjection molding unit and the second injection molding unit, the thirdmold including the position regulation part.
 12. The mold unit accordingto claim 11, wherein the third mold includes a mold that is used by anyof a temperature adjusting unit, the blow-molding unit, and an takingout unit of the resin container, the temperature adjusting unitadjusting a temperature of the preform or the molded object of the firstinjection molding unit.
 13. The mold unit according to claim 9, furthercomprising: a neck mold configured to be shared by at least the firstinjection molding unit and the second injection molding unit, grasp amolded object of the first injection molding unit, and convey the moldedobject to the second injection molding unit, wherein each of the firstcavity mold and the second cavity mold includes a position regulationpart that regulates a position of the neck mold.
 14. The mold unitaccording to claim 13, further comprising a third mold configured to beused in a process of the manufacturing apparatus that is different fromthe first injection molding unit and the second injection molding unit,the third mold including the position regulation part.
 15. The mold unitaccording to claim 14, wherein the third mold includes a mold that isused by any of a temperature adjusting unit, the blow-molding unit, andan taking out unit of the resin container, the temperature adjustingunit adjusting a temperature of the preform or the molded object of thefirst injection molding unit.